<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>定时器</title>
	<script type="text/javascript">
		window.onload = function(){
			var oPop = document.getElementById("pop");
			var oShut = document.getElementById("shout");
			setTimeout(showpop,3000);

			function showpop(){
				oPop.style.display = "block";
			}

			oShut.onclick = function(){
				oPop.style.display = "none";
			}
		}

	</script>
	<style type="text/css">
		.pop_con{
			display: none;
		}

		.pop{
			width: 300px;
			height: 300px;
			background-color: #fff;
			border: 1px solid #000;
			position: fixed;
			left: 50%;
			top: 50%;
			margin: -150px 0 0 -150px;
			z-index: 9999;
		}
		.mask{
			position: fixed;
			width: 100%;
			height: 100%;
			background-color: #000;
			left: 0;
			top: 0;
			opacity: 0.3;
			filter: alpha(opacity=30);
			z-index: 9990;
		}
	</style>
</head>
<body>
	<h1>首页</h1>
	<p>内容</p>






	<div class="pop_con" id="pop">
		<div class="pop">
			<h3>
				提示信息!
			</h3>
			<a href="" id="shout">关闭</a>
		</div>
		<div class="mask"></div>

	</div>
</body>
</html>